Abstract:
This study examined the modulatory effect of crude alkaloid extracts of bitter leaf (Vernonia
amygdalina) and water bitter leaf (Struchium sparganophora) on cognitive function, antioxidant
status, and activities of critical enzymes of monoaminergic, cholinergic and purigeneric systems of
neurotransmission in scopolamine-induced dementia rats. Cognitive impairment was induced in
Wistar rats pre-treated with alkaloid extracts of bitter and water bitter leaves by administration of
scopolamine (1 mg/kg body weight via i.p) for seven days. Prior to termination of the experiment,
the rats were subjected to spontaneous alternation (Y-maze) test to assess their spatial working
memory. Thereafter, activities of acetylcholinesterase (AChE), butyrylcholinesterase (BChE),
monoamine oxidase (MAO), NTPdases (ATPdase and ADPdase) and antioxidant enzymes (catalase
and Superoxide dismutase) of rat brain homogenate were determined. DPPH radical scavenging
ability of the alkaloid extracts showed that the bitter leaf extract had significantly higher (P>0.05)
inhibitory effect (3.01±0.02 μg/mL) when compared with water bitter leaf extract (2.78±0.05
μg/mcL), The extracts were also able to inhibit the activities of monoamine oxidase in
concentration dependent manner (0-26.67 μg/mL); however, the EC50 values reveals that alkaloid
extract from bitter leaf had a significantly higher (P>0.05) inhibitory effect (12.60±0.02 μg/mL)
when compared to that of water bitter leaf .Also, the iron chelating ability, ABTS scavenging
ability, malondialdehyde (MDA) and nitric oxide contents of the homogenate were determined. The
results showed that pre-treated rats significantly (p < 0.05) reversed the impairment in the rats
spatial working memory induced by scopolamine. Similarly, elevations in activities of AChE,
BChE, MAO and NTPdases altered by scopolamine when compared with control were significantly
(p < 0.05) reversed in rats with pre-treated with alkaloid extracts. This study has shown that
alkaloid extracts of bitter leaves has more antioxidative and neuroprotective effects more than the
water bitter leaves and hence, these vegetables could be used as a source of functional foods and
neutraceuticals for the prevention and management of cognitive impairments associated diseases
such as Alzheimer’s disease.
